Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing an article.
Description of the Related Art
One of apparatuses used in a manufacturing step (lithography step) for a semiconductor device or the like is an exposure apparatus which transfers the pattern of a mask onto a substrate. The exposure apparatus needs to accurately transfer the pattern of a mask onto a substrate. For this purpose, it is important to make the imaging plane (focus plane) of the projection optical system coincide with the substrate surface in the exposure apparatus. The exposure apparatus therefore performs focus measurement to measure the height of the substrate surface.
However, since a reaction force is generated along with acceleration or deceleration of the substrate stage in the exposure apparatus, the frame structure in the exposure apparatus is deformed and thereby an error in the result of focus measurement may be generated. It may become difficult to accurately transfer the pattern of a mask onto a substrate. Japanese Patent Laid-Open No. 9-199386 has proposed a method of measuring in advance the shift amount of an image projected on a substrate in accordance with the acceleration of a substrate stage, and when exposing the substrate, applying the shift amount as a correction value to the result of focus measurement. Japanese Patent Laid-Open No. 2011-238707 has proposed a method of obtaining in advance, as a correction value, the difference between results of focus measurement during acceleration and constant-speed movement of a substrate stage, and correcting, based on the correction value, the result of focus measurement during acceleration of the substrate stage.
In general, the exposure apparatus exposes a plurality of shot regions on a substrate while correcting the result of focus measurement based on a correction value obtained in advance in accordance with the acceleration of the substrate stage. However, a shot region (unexposed shot region) which has not been exposed because the exposure condition was not satisfied till the start of exposure may be generated among a plurality of shot regions. To increase the yield, even the unexposed shot region needs to be exposed. When exposing the unexposed shot region, a correction value obtained in advance is desirably applied. Therefore, when exposing the unexposed shot region, the substrate stage should be driven in the same way as that when a plurality of shot regions were exposed in order.